Animal guard for electrical equipment



June 24, 1958 H. c. MARCROFT ANIMAL GUARD FOR ELECTRICAL EQUIPMENT FiledApril 13, 1954 ATTORNEYS United StatesPatent O ANIMAL GUARD FORELECTRICAL EQUIPMENT Harold C. Marcroft, Baltimore, Md.

Application April 13, 1954, Serial No. 422,767

3 Claims. (Cl. 174-140) This invention relates to insulators orelectrical bushings such as used on transformers, circuit breakers,capacitors, and the like, and in particular a disc of ceramic, plastic,or other suitable material having a conducting band providing a rimaround the outer edge and having an impedance, such as a resistor orcondenser connecting the band with a clamp or other means to theelectricalconducting stud of the bushing.

The purpose of this invention is to reduce damage to electrical bushingsdue to an electric power are caused by a flash of lightning or by ananimal standing upon a tank of the apparatus and touching the bushingcap, where the electric system in which the parts are included isgrounded at some part of the installation, such as the neutral terminalof an associated transformer, in a system known as a grounded neutralsystem.

An animal standing on the tank of a transformer or the like and touchingthe bushing cap causes an electric power are or short circuit whichdamages both the bushing, the cap of which is engaged by the animal andsimilar bushings of associated equipment, and consequently, causesextensive power interruptions. With this thought in mind this inventioncontemplates a shield or guard positioned over the live cap at the upperend of an electrical bushing, the rim of which guard is connected by animpedance to the main stud of the bushing, whereby the possibility of ananimal standing on the tank of the equipment and touching the bushingcap or live conductors is substantially eliminated.

The object of this invention is, therefore, to provide means for formingand installing guards or protecting shields over electrical bushings ofa transformer or the like whereby an animal, such as a squirrel willengage a guard or shield instead of the bushing.

Another object of the invention is to provide a guard for preventinganimals contacting electrical equipment in which the guard is adapted tobe installed on equipment now in use.

Another important object of the invention is to provide a protectingguard for an electrical bushing whereby beneficial eifects fromlightning flashovers are attained and wherein an animal contacting theguard is killed or receives a severe jolt so that the possibility offurther attempts to contact the bushing is substantially eliminated.

A further object of the invention is to provide an animal guard forelectrical equipment, such as bushings in which the device is of asimple and economical construction.

With these and other objects and advantages in view the inventionembodies a disc of insulating material having a continuous conductingband on the peripheral edge with clamping elements secured to the discand adapted to suspend the disc from the bushing stud or cap, and aresistance or other impedance connected between the band and the mainconnection of the bushing, by a clamp or otherwise.

Other features and advantages of the invention will appear from thefollowing description taken in connection with the drawing, wherein:

Figure 1 is a plan view looking downwardly upon the upper end of anelectrical bushing showing a guard positioned over the bushing and alsoshowing the guard with a rim thereof connected by means of an impedanceto the terminal of the bushing,

Figure 2 is a side elevational view of the electric bushing shown inFig. 1 showing a guard mounted on the bushing, the guard and clampingelements thereof being shown in section, and the parts being shown on anenlarged scale.

Figure 3 is a side elevational view similar to that shown in Fig. 2illustrating a modification where the impedance or resistance isreplaced with a conducting glaze on the upper surface of the guard andwherein the parts are shown on a reduced scale.

Referring now to the drawing wherein like reference characters denotecorresponding parts the improved electrical bushing or insulator guardof this invention ineludes a disc 10 of insulating material having a rim11 of material providing a good electrical conductor extended around theperipheral edge, a cup-shaped element formed with sections 12 and 13clamped to a terminal or stud 14 of a bushing 15 and a resistance orother impedance 16 connected to the rim 11 by brazing or the like orwith a bolt or rivet 17, and also connected to the electrical conductingstud 14 such as by a bolt 18 of a clamp formed with U-shaped sections 19and 20 and secured in clamping relation with the stud with bolts 21 and22, the bolt 21 extending through flanges 23 and 24 and the bolt 22through flanges 25 and 26.

The edge of the section 12 of the supporting element of the disc 10 isconnected to the insulator by suitable means, such as with a flange 27that is embedded in the disc 10 and in this arrangement the upper partof the section is provided with flanges 28 and 29 that are secured tocorresponding flanges 30 and 31 of the section 13 with bolts 32 and 33.The lower edge of the section 13 is also provided with a flange 34 thatis embedded in the material of the disc 10.

In the design illustrated in Figure 3 a disc 35 having a rim 36 issecured to a stem 37 of a bushing 38 with clamping elements 39 havingbolts 49 and 41 extended therethrough, similar to the elements 12 and 13whereby the disc 35 is secured over the insulator or bushing. In thisdesign the upper surface of the disc 35 is coated with a glaze, asindicated by the numeral 42 which provides resistance thereby performingthe function of the resistance of impedance 16, of the design shown inFigures 1 and 2.

The guard may be provided in different designs to cover insulators orbushings of different types and designs and the guards may be securedover the bushings or insulators by other suitable means. Other means mayalso be used for providing resistance or impedance to replace theresistance 16 or the glaze 42.

It will be understood that other modifications, within the scope of theappended claims, may be made in the design and arrangement of the partswithout departing from the spirit of the invention.

What is claimed is:

1. In a guard for electrical equipment, the combination which comprisesan insulator including a bushing having a plurality of sections andhaving a stem extended upwardly therefrom, a cup-shaped element mountedon the stem and extended over the inner hub portion of the uppermostsection of said bushing, a disc of insulating material carried by thecup-shaped element, a rim of material capable of conducting electricitymounted on the periphery of the disc, a clamp secured to the stern 3 rand spaced upwardly above the upper end of the bushing, and an impedanceextended from the rim of the disc to the clamp on the stem of thebushing.

I In a guard for electrical equipment, the combination which comprisesan insulator including a bushing having a plurality of sections andhavinga stem extended upwardly therefrom, a split cup-shaped elementmounted on the stem and extended over the inner hub portion of theuppermost section of said bushing, said cup-shaped element having aflange extended from the lower edge, a

disc of insulating material positioned on the flange of the V cup-shapedelement and extended horizontally therefrom, a rim of material capableof conducting electricity mounted on the periphery of the disc, a clampsecured to the stem and spaced upwardly above the upper end of thebushing, and an impedance extended from the rim of the disc to the clampon the stem of the bushing.

3. A guard for insulators or electrical bushings comprising a disc ofinsulating material, a continuous rim of conductive material extendedaround the peripheral edge 20 0f the disc and overlapping the edges ofupper and lower surfaces thereof, a stud extended upwardly from thecentral portion of the bushing, an inverted cup-shaped element extendedupwardly from the central portion of the disc, over the central portionof the bushing, and positioned to be clamped around the stud extendedupwardly from the bushing for suspending the disc above and in spacedrelation to the bushing, a clamp mounted on the stud and spaced upwardlyfrom the inverted cup-shaped element, and a resistance positioned withthe upper end connected to the clamp spaced above said invertedcupshaped element and with the lower end connected to the rim on theperiphery of the disc.

References Cited in the file of this patent UNITED STATES PATENTS1,166,393 Steinberger Dec. 28, 1915 1,766,636 Holzel June 24, 1930FOREIGN PATENTS 813,720 Germany Sept. 17, 1951

